The invention relates to a device for dewatering and/or washing suspensions, especially fibre stock suspensions, with two dewatering rolls rotating in opposite directions, where at least a further two guide rolls, especially press rolls, are provided and an endless woven wire or filter belt runs over each combination of one dewatering roll and one further guide roll, by which arrangement the suspension to be dewatered and/or washed is carried in the gap between the two belts and dewatered.
The devices already known have, in some cases, only two dewatering rolls rotating in opposite directions or are so-called twin wire dewatering units in which additional guide rolls and suitable wire or filter belts for dewatering are provided in addition to the dewatering rolls. Furthermore, the converging wire or filter belts run horizontally in most of these devices. Such devices can be used advantageously for dewatering, especially dewatering of fibre stock suspensions, blat have no facility for washing the suspension. If the suspension sometimes has to be washed and at other times is required without being washed for different application, large scale adjustments or modifications have to be made when using the devices already known.
EP-A-0 454 989 describes a vertical former with various form elements, where the suspension is injected into the gap between the belts. The first dewatering takes place in the roll gap or slot.
EP A-0 311 834 describes a dewatering device where sludge, fruits and vegetables or waste of pressed fruits or vegetables are dewatered by dewatering cogwheels. Here the material to be dewatered is fed through a chute arranged above the cogwheels, and falls onto the cogwheels and the belts. The belts are driven around the respective cogwheel, a deflecting roll and a (belt) dewatering roll. Important for this document is that the belts are driven together only on a short distance to reduce the wear.
U.S. Pat. No. 3,915,865 describes a dewatering device where the sludge is first led along a horizontal path while being dewatered by gravity. Then the belts are deflected by press rolls and guided together to a vertical gap from top to bottom.